Inserts for directing molding compound flow and semiconductor die assemblies

ABSTRACT

Flow diverting structures for preferentially impeding, redirecting or both impeding and redirecting the flow of flowable encapsulant material, such as molding compound, proximate a selected surface or surfaces of a semiconductor die or dice during encapsulation are disclosed. Flow diverting structures may be included in or associated with one or more portions of a lead frame, such as a paddle, tie bars, or lead fingers. Flow diverting structures may also be inserted into a mold in association with semiconductor dice carried on non-lead frame substrates, such as interposers and circuit boards, to preferentially impede, redirect or both impede and redirect the flow of molding compound flowing between and over the semiconductor dice.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/484,493, filed on May 31, 2012, now U.S. Pat. No. 8,399,966, issuedMar. 19, 2013, which is a continuation of U.S. patent application Ser.No. 13/048,110, filed Mar. 15, 2011, now U.S. Pat. No. 8,207,599, issuedJun. 26, 2012, which is a divisional of U.S. patent application Ser. No.11/526,520, filed Sep. 25, 2006, now U.S. Pat. No. 7,927,923, issuedApr. 19, 2011, the disclosure of each of which is hereby incorporatedherein by this reference in its entirety.

BACKGROUND

Field of the Invention. Embodiments of the present invention relategenerally to the packaging of semiconductor dice. More particularly,embodiments of the present invention relate to methods and apparatus forredirecting a flow of a molding compound, such as a resin, in a moldcavity, and resulting semiconductor device packages.

State of the Art. Semiconductor dice are created from wafers, such assilicon wafers, as well as from other bulk semiconductor substrates,using a sequence of material deposition and removal acts that are wellknown to those of ordinary skill in the art. Ultimately, the completedsemiconductor dice may be packaged for many applications byencapsulating one or more semiconductor dice in a resin-based moldingcompound comprising, conventionally, a silicon particle-filledthermoplastic resin.

One approach to packaging of semiconductor dice utilizes a lead frame.Lead frames are generally thin metallic layers, although metal-coatedpolymer film lead frames are also known. In the center of some leadframes is a so-called “die paddle” upon which one or more semiconductordice may be mounted, such as by an adhesive or a solder. Lead fingers,or leads, are disposed adjacent one or more sides of the die paddle. Thepaddle is isolated from the remainder of the lead frame except bymembers called tie bars, which are used to initially support the leadframe when in strip form with other identical lead frames, beforeencapsulation of the die or dice and a subsequent trim and formoperation wherein the lead frame lead fingers as well as the die paddleare severed from a surrounding, supporting structure. The lead fingers,when a lead frame is in strip form and during encapsulation of asemiconductor die or dice carried thereon, are separated from each otherby intervening, supporting dam bars, which are also severed during thetrim and form operation.

Once a semiconductor die is secured to the die paddle and wire-bonded orotherwise electrically connected to the lead fingers, each resultingassembly, in strip form with a plurality of identical assemblies, isthen placed in a mold cavity of a plurality of mold cavities definedbetween opposing segments of a mold of a transfer molding apparatus.Molten molding compound, comprising the aforementioned siliconparticle-filled thermoplastic resin, is injected under pressure into themold cavity to encapsulate and form a package around the semiconductordie and the plurality of lead fingers. The packaged semiconductor die isremoved from the mold and separated from the lead frame in theaforementioned trim and form operation, wherein the lead fingers mayalso be conventionally formed into a final configuration to facilitateconnection of the outer ends thereof to higher-level packaging. Thepackaged semiconductor die is then available for use, such as inmounting to a printed circuit board (PCB) or to other higher-levelpackaging.

Other lead frame configurations, include a so-called “leads-over-chip”(LOC) configuration, wherein no die paddles are employed and leadfingers of a lead frame are adhered to an active surface of asemiconductor die with inner ends thereof proximate a central row orrows of bond pads. A similar configuration, known as a“leads-under-chip” (LUC) configuration, likewise does not employ a diepaddle, and the lead fingers extend under and are adhered to a back sideof a semiconductor die. Another configuration is a so-called“leads-between-chip” configuration, wherein a lead frame (with orwithout a die paddle) is interposed between semiconductor dice onopposing sides thereof. The encapsulation process, followed by trim andform, is generally the same for these semiconductor device assemblyconfigurations as for die paddle-type assemblies.

A problem with current packaging processes is that mold cavityconfigurations and tolerance variances, semiconductor die shapes andsizes, the presence of more than one semiconductor die to beencapsulated, and the configuration and orientation of the lead frameelements may lead to uneven flow of resin inside a mold cavity,resulting in an uneven distribution of resin around the semiconductordie or dice and the lead frame in the mold cavity. The resulting voids,knit lines, and pinholes in the resin encapsulant structure cancompromise the integrity of the packaging around the semiconductor dieor dice and can also adversely affect heat transfer characteristics ofthe package.

To further explain how the aforementioned defects may occur, aconventional mold comprises a plurality of mold cavities defined betweena top mold plate and a bottom mold plate. The semiconductor diceassembled with, and electrically connected to, lead frames carried by asupporting structure of a lead frame strip, are disposed in the moldcavities with the supporting structure outside the cavities andconnected to the assemblies by tie bars and lead fingers. The moldingcompound is introduced into each mold cavity through one or more“gates,” or openings, leading to the mold cavity, generally from oneside of the mold cavity and displacing air in the mold cavity outthrough one or more apertures, also termed “vents,” in the opposing sideof the mold cavity, although vertically oriented mold cavities areknown. In any case, the aforementioned variables in the mold cavities aswell as in the semiconductor die assemblies placed therein may cause theflow front of the pressurized molding compound to accelerate around thesides of each assembly, particularly if the assemblies include a stackof semiconductor dice, leaving the top and bottom of the stacksinadequately encapsulated. This phenomenon is due to the relativedifference in resistance to molding compound flow provided by therelatively larger cross-sectional areas to the sides of the die stackprovided by the mold cavity in comparison to the smaller cross-sectionalareas, above and below, and between the die stack and the mold cavitywalls.

Additionally, semiconductor dice and their corresponding connectionswith the lead frames may be modified over time. A mold cavity may havebeen optimally designed to avoid the formation of voids in an initiallead frame configuration of a package for a certain semiconductor die ordie stack. However, when the semiconductor die is modified such that thesize or shape of the die has changed (for example, when die “shrinks”are implemented from one generation of a die to the next, to increaseyield per wafer), then voids may form in the encapsulant due to a changein the flow pattern thereof during transfer molding. As retooling themold plates may cost well in excess of one hundred thousand dollars, itwould be desirable to be able to beneficially modify the flowcharacteristics of resin within a mold cavity without having to modifythe mold cavity itself. Several attempts to solve this problem bymodifying a lead frame characteristic have been made.

One attempt to control the flow of resin in a mold cavity has been tokink, cut, or bend a tie bar adjacent to a gate of the mold cavity.Another approach has been to form an offset in a lead frame, such as ina tie bar, close to a gate to affect the flow of resin entering the moldcavity. Both approaches are limited to controlling the amount of resinthat flows across the top or bottom surface of a lead frame.Additionally, both approaches are limited to being located near a gateof a mold cavity.

A third approach has been to include an additional hole in a lead frameto allow resin to flow into a top portion of a mold cavity beforeflowing into a bottom portion. However, this approach is unable tomodify a flow of resin within the mold cavity once the resin has leftthe gate area of the mold cavity.

A fourth approach has been to extend a region of a lead finger of a leadframe, where the extended region is in the same plane as the lead fingerand the remainder of the lead frame. The extended region is close to thegate of the mold cavity and purportedly results in a more evendistribution of resin across the top and bottom of the lead frame. Thisapproach, again, requires that the extended region must be close to thegate of the mold cavity.

A fifth approach has been to modify the flow of resin on a leadfinger-by-lead finger basis. In this approach, the ends of the leadfinger may be down-set similar to the down-set of the die paddle of alead frame. A lead finger may then be wire-bonded to the semiconductordie. The resulting vertically oriented portion of the lead fingerpurportedly reduces the flow rate of resin right at the bonding point ofa wire to the end of the lead finger. The fifth approach also involvesforming a second wire ball to cover the heel of the wire bond connectinga lead finger and a semiconductor die. A second wire is attached to thesecond wire ball and to the lead finger. The second wire and the secondball serve to retard the flow of resin at the lead finger wire bondingpoint. The fifth approach is generally not viable for solving theproblem of voids, pinholes, and knit lines in a package.

A sixth approach includes the use of a flow diverter positioned adjacenta flow hole in a lead frame. The flow diverter is positioned to increasethe volume of material that passes through the flow hole and underneaththe lead frame.

A need exists in the art for a lead frame that may be modified in a widevariety of locations to restrict and redirect the flow of resin within amold cavity. A further need exists to control the flow rate of resinaround the sides of a semiconductor die stack.

Heretofore, the packaging of semiconductor dice has been discussed inthe context of lead frame-mounted dice. However, some semiconductor diceor chips are packaged after mounting the chip onto a substrate, such asa printed circuit board (PCB). For example, with so-called “flip-chips,”the active surface of the semiconductor die bears solder balls or otherdiscrete conductive elements protruding therefrom, which serve tomechanically and electrically connect the semiconductor die to asupporting substrate. A flip-chip may be underfilled with a flowabledielectric material to surround the space between and around thediscrete conductive elements. The flip-chip may then be wholly orpartially encapsulated in a packaging resin, or the encapsulationperformed concurrently with the underfill.

Additionally, semiconductor dice may be mounted directly to substratesother than lead frames, such as to interposer substrates in achip-on-board (COB) or board-on-chip (BOC) structure, which may beconfigured as, for example, ball-grid-array (BGA), pin-grid-array (PGA)or land-grid-array (LGA) packages. For example, a number ofsemiconductor dice may be mounted to an array of unsingulated interposersubstrates disposed within a mold cavity, and then resin flowed over thesurface of the interposer substrates to encapsulate the dice andconductive elements, such as wire bonds, electrically connecting thesemiconductor dice to the interposer substrates. Once the resin iscured, the individual encapsulated semiconductor dice mounted to theirrespective interposer substrates may be separated, or “singulated,” fromeach other.

Generally, whenever a molding compound such as a thermoplastic resin orother flowable dielectric material is forced to flow over or around alead frame or other substrate with one or more semiconductor dicemounted thereto within a mold cavity, the resin may flow faster aroundthe sides of the dice than over and under the dice. This may result invoids forming over the tops and bottoms of some of the semiconductordice, particularly the semiconductor dice in a mold cavity farthest fromthe resin entry point. A need exists in the art to reduce the flow ofresin in between the dice to avoid the formation of voids and otherdefects in the packaging encapsulant.

BRIEF DESCRIPTION OF THE DRAWINGS

A more particular description of the invention briefly described abovewill be rendered by reference to specific embodiments thereof, which areillustrated in the appended drawings. Understanding that these drawingsdepict only embodiments of the invention and are not therefore to beconsidered limiting of its scope, the invention will be described andexplained with additional specificity and detail through the use of theaccompanying drawings in which:

FIG. 1 illustrates a conventional paddle-die set without the benefit ofembodiments of the present invention;

FIG. 2 illustrates an embodiment of the invention where the tie bars ofthe paddle-die set of FIG. 1 have been modified to include baffles;

FIG. 3 illustrates an embodiment of the present invention where a paddlehas been modified to include one or more baffles;

FIG. 4 illustrates embodiments of the present invention where both apaddle and a lead finger have each been modified with a baffle;

FIG. 5 illustrates an embodiment of baffle attachment to a paddle-dieset;

FIGS. 6A through 6D illustrate embodiments of a baffle;

FIGS. 7A through 7D illustrate embodiments of a baffle;

FIG. 8A illustrates an array of semiconductor dice placed on asubstrate;

FIG. 8B illustrates the wire bonding of the semiconductor die of FIG. 8Ato the substrate;

FIG. 8C illustrates flow fronts of resin flow across the substrate ofFIG. 8B during encapsulation of the semiconductor dice;

FIG. 8D illustrates modification of the flow fronts of FIG. 8C using agrid structure including baffles according to an embodiment of thepresent invention;

FIG. 9 is an enlarged view of a grid structure including baffles, asemployed in the embodiment shown in FIG. 8D;

FIGS. 10A through 10D illustrate various baffle configurations suitablefor use in the grid structure of FIG. 9; and

FIG. 11 illustrates an embodiment of the present invention in thecontext of a leads-over-chip semiconductor device assembly.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention may be utilized with lead frames,interposer substrates, circuit boards, or in any other application wherea flowable packaging material tends to flow around the sides of asemiconductor die or dice rather than over and/or under the die or diceduring an encapsulation operation conducted using a mold cavity or groupof mold cavities. Embodiments of the present invention may be employedto modify the hydraulic characteristics of flowable packaging materialconfined by a mold cavity as it passes therethrough to encapsulate asemiconductor device assembly placed therein.

In accordance with one embodiment of the present invention, as broadlydescribed herein, the present invention may comprise a lead frame forpackaging a semiconductor die or dice. The lead frame comprises at leastone support member adapted for connection to the die, the at least onesupport member including an enlarged portion adjacent a perimeter of thesupport member and outside of the footprint of the die mounted thereto,the enlarged portion having at least a portion thereof configured forselective orientation in a non-parallel orientation to a plane of thesupport member or in some other, substantially non-parallel orientationto an intended direction of flow of molding compound duringencapsulation of the die or dice. The at least a portion of the enlargedportion may be so selectively oriented during fabrication of the leadframe, or thereafter, to provide a barrier effective to impede flow ofmolding compound. Such lead frames in strip form also compriseembodiments of the invention.

In accordance with another embodiment of the present invention, thepresent invention may comprise a lead frame for packaging asemiconductor die or dice. In this embodiment, the lead frame maycomprise a member other than a support member such as, withoutlimitation, a lead finger or a tie bar, comprising an enlarged portionhaving at least a portion thereof configured for selective orientationin a non-parallel orientation to a major plane of the lead frame or insome other, substantially non-parallel orientation to an intendeddirection of flow of molding compound during encapsulation of the die ordice. The at least a portion of the enlarged portion may be soselectively oriented during fabrication of the lead frame, orthereafter, to provide a barrier effective to impede flow of moldingcompound. Such lead frames in strip form also comprise embodiments ofthe invention.

Another embodiment of the present invention comprises a method ofpackaging a semiconductor die or dice, the method comprising flowing amolding compound over and around a semiconductor die or dice whileselectively impeding the flow of a portion of the molding compoundaround the sides of the semiconductor die or die stack to cause enhancedflow of another portion of the molding compound across at least one of atop surface and a bottom surface of the semiconductor die or dice.

A further embodiment of the present invention comprises a moldingcompound flow diverting device for use in encapsulation of semiconductordice carried on a substrate other than a lead frame, the devicecomprising a grid structure including a plurality of interconnectedbaffles and optionally, a plurality of support members. The gridstructure may be adapted to engage the substrate, to be engaged by themold plates, or both.

In each of the embodiments of the invention, the flow rates of moldingcompound past various sides of a semiconductor device assembly may beequalized or otherwise modified to preclude a shortage of moldingcompound in a given area of a mold cavity. Similarly, when moldingcompound is being flowed past a number of semiconductor dice orsemiconductor device assemblies in serial fashion, embodiments of thepresent invention may be selectively placed and oriented to providesubstantially uniform coverage by the molding compound within a moldcavity or a group of mold cavities.

Semiconductor device assemblies fabricated in accordance withembodiments of the invention are also encompassed thereby.

These and other features and advantages of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of the invention as set forthhereinafter.

In the drawing figures, like numbers describe like elements. Wheneversimilar elements are alphabetically differentiated, such as “100 a,”“100 b,” “100 c,” etc., and reference is made without a letter, such as“100,” then the broad class of the element, which includes all of thealphabetically differentiated variations, is referenced. The terms“resin” and “molding compound,” as the term is used herein, encompassesany flowable molding or encapsulation compound, whether or notcharacterized in the chemical sense as a resin per se, as well as otherflowable packaging materials known in the art.

FIG. 1 illustrates a conventional lead frame without the benefit ofembodiments of the present invention. A semiconductor die 60 (or stackof dice 60) is mounted on the two paddles 50 a and 50 b of a lead frame10, which are supported from the periphery of the lead frame strip byties bars 30, as is conventional. Of course, lead frames with singlepaddles, quad paddles or other paddle variations may experience similardeficiencies in encapsulant integrity. Lead frame 10 includes aplurality of lead fingers 20 adjacent the peripheries of paddles 50 aand 50 b, lead fingers 20 being laterally joined by dam bars 12, as isconventional. As shown, paddles 50 a and 50 b have been down-set at 31with respect to lead fingers 20, as is conventional. Lead frame 10 maybe placed in a mold cavity defined between two segments or plates of amold, where the mold cavity defines the exterior surface of package 80.Resin 70 may be injected through runner 17 and gate 16 into the moldcavity (periphery not shown) in which lead frame 10, bearingsemiconductor die or dice 60, is disposed. It is desirable for resin 70to fill the entire mold cavity volume between the semiconductor dieassembly and the inner wall of the mold cavity without forming knitlines, pin holes, or voids. FIG. 1 illustrates where resin 70, aftercontacting front surface 61 of semiconductor die or dice 60, followsflow path 72 and 73 around the side 62 and side 64 of semiconductor dieor dice 60 and past rear surface 63 thereof. Resin 70 then exits outvent 18 without a sufficient portion thereof flowing over the top ofsemiconductor die 60 or underneath paddles 50 a and 50 b, resulting inunacceptable voids in the resin 70 in those areas, compromisingpackaging integrity.

In FIG. 2, lead frame 110 has been modified with embodiments of thepresent invention, which are adaptable to virtually any lead frameconfiguration. It will be appreciated by one of ordinary skill in theart that one, some, or all of the embodiments of lead framemodification, as depicted in FIG. 2, may be employed with a lead frameof any given configuration. Tie bars 30 have been modified to includebaffles 35 a through 35 f. In FIG. 2 as in FIG. 1, paddles 50 a and 50 bhave been down-set as shown by down-set marks 31 of the tie bars 30.Baffles 35 a through 35 f, as shown in FIG. 2, have not yet been angledor rotated out of a plane substantially parallel to the lead frame 110(and, thus, to the direction of resin flow) in accordance withembodiments of the present invention. The angling of the baffles 35 athrough 35 f may occur at any time, such as before, during, or after thedown-set of the paddles 50 a and 50 b. The same down-set tool may beused to angle baffles 35 a through 35 f. Any other conventional tool ordevice as known in the art for bending lead frames may be used.Alternatively, baffles 35 a through 35 f may be formed in an angledposition during initial fabrication of lead frame 110. Baffles 35 athrough 35 d are all similar and the elements of baffle 35 d are alsopresent in baffles 35 a, 35 b, and 35 c. For reference purposes, itshould be noted that baffle 35 d, as an example of baffles 35 a through35 f, includes a first baffle element 36 d, support member 38 d, and asecond baffle element 37 d, the other baffles including like elements,similarly numbered. Baffles 35 thus may be selectively placed, sized andoriented to impede flow of resin 70 through areas of largercross-section, for example along the sides of a semiconductor die orplurality of dice so that more resin 70 flows across, again by way ofexample only, a top or bottom surface of the semiconductor die or groupof dice. Stated another way, the flow rate of resin 70 may be modifiedin selected areas so that the overall resin flow front is maintained ata more constant rate, rather than one portion thereof movingsubstantially ahead of another portion, resulting in voids and otherdefects in the encapsulant package being formed.

FIGS. 7A through 7D illustrate a few embodiments of how baffles 35 athrough 35 d may be configured prior to the transfer molding process.FIGS. 7A through 7D refer generically to baffles such as, but notlimited to, those of FIG. 2. In FIG. 7A, a baffle 175 a has been twistedso that the baffle 175 a is no longer in a horizontal plane parallel toresin flow, but is more vertical, substantially transverse to resinflow. In this particular embodiment, first baffle element 176 a is inline with support member 178 a and second baffle element 177 a, suchthat baffle 175 a essentially presents a flat surface. Baffle 175 a maybe inclined at any angle and does not have to be perpendicular (i.e.,vertical), the angle of inclination being selected for the relativedegree of resin flow impedance desired. FIG. 7B illustrates anotherembodiment of baffle 175 b where first baffle element 176 b and secondbaffle element 177 b are in parallel planes, but support member 178 bremains in a horizontal plane, creating a step-like configuration. FIG.7C illustrates an embodiment where baffle 175 c is configured in a “V”or chevron, shape and support member 178 c is reoriented transverse toresin flow. In a particular embodiment, as illustrated in FIG. 7D,support member 178 d may be the same width “w” as the remainder of a tiebar 30 (FIG. 2). FIG. 7D illustrates an embodiment of baffle 175 d wherefirst baffle element 176 d and second baffle element 177 d are bent at alocation other than the edge of support member 178 d, support member 178d being reoriented transverse to resin flow.

First baffle elements 176 and second baffle elements 177 may include anydesired number of steps and bends. In FIGS. 7A through 7D, the firstbaffle elements 176 and second baffle elements 177 are all shown ashaving flat surfaces. However, first baffle elements 176 and secondbaffle elements 177 may also be shaped with arcuate portions. FIGS. 7Athrough 7D illustrate a few embodiments of how a baffle may be modifiedor formed. Baffles 175 may be formed by etching or stamping as usedconventionally in lead frame fabrication, and then cut, twisted, bent,or modified to function in accordance with embodiments of the presentinvention.

Referring once again to FIG. 2, tie bars 30 e and 30 f illustrate thattie bars 30 may be modified to provide increased structural support tobaffles 35 e and 35 f, respectively. A tie bar 30 may be modified in anymanner desirable to support baffles 35. Baffles 35 e and 35 f are shownprior to any reconfiguration of one or more portions of the baffles outof a horizontal or other plane substantially parallel to moldingcompound flow. The discussion regarding the baffle embodiments andconfiguring thereof, as shown in FIGS. 7A through 7D, apply equally tobaffles 35 e and 35 f. Baffles 35 a through 35 f illustrate only twoembodiments of the present invention. A tie bar 30 may be modified toinclude an enlarged, baffle portion in any manner. Likewise, theenlarged, baffle portion may be bent, twisted, or otherwise modified inany manner suitable to restrict the flow of resin 70 and desirablyredirect the flow of resin 70. In particular, a tie bar 30 may bemodified in any manner such that resin 70, in addition to flowing alongflow paths 72 and 73, also flows along flow path 75 across a top surfaceof semiconductor die 60 and along flow path 74 underneath semiconductordie 60 and paddles 50 a and 50 b. Additionally, a tie bar 30 may bemodified in conjunction with the modification of a die paddle 50 tocreate an appropriate baffle.

It should be noted with reference to FIG. 2 that lead fingers 20, andany corresponding bond wires (not shown) extending between lead fingers20 and semiconductor die or dice 60, may be orientated substantiallytransverse to a flow path 72, 73 of resin 70.

FIG. 3 illustrates a particular embodiment of the invention, wherein adie paddle 50 may be modified to incorporate baffles 55 a and 55 b.Baffles 55 a and 55 b may be made from existing material of die paddle50 or die paddle 50 may be elongated or otherwise enlarged for thepurpose of providing baffles 55 a and 55 b. Baffle 55 a includes firstbaffle element 56 a, support member 58 a, and second baffle element 57a. Baffle 55 b, as shown, includes first baffle element 56 b, supportmember 58 b, and second baffle element 57 b. Baffle 55 a and baffle 55 bmay be similar or different, although in symmetrical packages they maygenerally be identical in structure and configuration. Alternatively,only a single baffle 55 a or 55 b may be used, in some packageconfigurations. Baffles 55 a and 55 b may be of any suitable width. Leadfingers 20 are shown adjacent baffle 55 b. Lead fingers 20 may also lieadjacent baffle 55 a, as well as adjacent the other sides of die paddle50, such as in a quad flat package (QFP) configuration. In FIG. 3, theheight of first baffle element 56 a is less than the height of the stackof semiconductor dice 60; however, the height of first baffle element 56a is not limited. In a particular embodiment, the height “h” of firstbaffle element 56 a is governed by the length “l” of support member 58a, which may be upset out of a horizontal or other plane substantiallyparallel to molding compound flow. However, in other embodiments, theheight “h” of first baffle element 56 a is not determined by or is notaffected by the length “l”. Similarly, the width of first baffle element56 a may be the same as the width “w” of support member 58 a or they maybe different. The same variations may apply with respect to secondbaffle element 57 a.

In a particular embodiment, the thickness “t” of baffle 55 a is the sameas the thickness of die paddle 50. In other embodiments, the thicknessof baffle 55 a may be greater or less than that of die paddle 50. Forexample, baffle 55 a may be laminated with a support layer to increasethe rigidity of baffle 55 a. Baffle 55 a may also include support ridgestransverse to the major plane thereof to increase the rigidity. Secondbaffle element 57 a and first baffle element 56 a may be horizontallyseparated from die paddle 50 by a lateral gap 51, as shown. Gap 51 maybe as narrow or as wide as desired to promote resin flow adjacent to thestack of semiconductor dice 60. Baffle 55 a may be as wide as desirableto provide the necessary adjustment to the flow rate of resin flowingaround the side of semiconductor die 60. As the width “w” of baffle 55 aincreases, the length of the bond wires 40 connecting semiconductor die60 to lead fingers 20 must increase. However, process parameters may bemodified to avoid wire sweep with the longer bond wires and sweep is notperceived to be a significant problem.

First baffle element 56 a and second baffle element 57 a may be bent ortwisted by a down-set tool during the packaging process. Alternatively,first baffle element 56 a and second baffle element 57 a may be formedperpendicular or at some other angle to support member 58 a at the timethe lead frame is formed. Even though the height “h” of first baffleelement 56 a is not a limiting factor, it will generally be undesirablefor first baffle element 56 a or second baffle element 57 a to contact amold cavity wall, unless it is desirable to employ same to stabilize thelead frame in the mold cavity.

The discussion regarding baffle 55 a may apply equally to baffle 55 b.Four semiconductor dice 60 are illustrated in FIG. 3, to form a quad diepackage (QDP). Only a single semiconductor die 60 may be employed in apackage, or some other number of semiconductor dice 60.

Referring to FIG. 3, as resin (not shown) flows against front surfaces61 and around sides 64 of semiconductor dice 60, first baffle elements56 a and 56 b and second baffle elements 57 a and 57 b impede the resinflow and reduce the resin flow rate around the sides 64 of semiconductordice 60. These restrictions placed adjacent the sides 64 ofsemiconductor dice 60 tend to induce a flow of resin over the top ofuppermost semiconductor dice 60 and underneath die paddle 50. Baffles 55a and 55 b may be located on any suitable side or sides of semiconductordie 60 in positions that do not interfere with wire bonding to leadfingers 20. In a particular embodiment, baffles 55 may be placedadjacent all four sides of semiconductor dice 60.

First baffle element 56 a is shown perpendicular to support member 58 aas is second baffle element 57 a; however, first baffle element 56 a maybe inclined at any suitable angle relative to support member 58 a. In aparticular embodiment, first baffle element 56 a is disposed at a 110degree included angle relative to support member 58 a and second baffleelement 57 a may be inclined to the same orientation.

FIG. 4 illustrates an embodiment where a baffle 155 a extends in frontof front surfaces 61 of semiconductor dice 60 while baffle 55 b islocated on the side, as in FIG. 3. In FIG. 4, baffle 155 a only includesa first baffle element 56 a. FIG. 4 further illustrates that multiplebaffles 55 b and 155 a may be present, but do not need to be symmetricalor symmetrically placed. For example, where a resin 70 (not shown)exhibits a greater flow rate around side 62 of semiconductor die 60 thanit does around side 64, then a baffle 55 b may only be necessary aroundthe side 62 of semiconductor die 60. Die paddle 50 may be enlarged andmodified in any manner necessary or desirable to provide baffles torestrict the flow rate of a resin 70. The configurations of baffles 175of FIGS. 7A through 7D apply equally to baffles 55 b and 155 a. Inaddition to modifying the tie bars 30 or paddles 50 to provide a flowrestriction device, a lead finger 20 may also be modified, as shown.

As shown in FIG. 1, an individual lead finger 20 may be a hot lead 21, aground lead 22, or a dummy lead 24. A portion of the length or all ofthe length of a lead finger 20 may be enlarged to serve as a baffle forrestricting the flow of resin 70. This enlarged portion may be twistedduring the packaging process to serve as a baffle or may be formed inposition at the time the lead frame is formed. FIG. 4 illustrates anembodiment where a lead finger 20 has been modified to include a baffle25, and adjacent foreshortened dummy leads truncated to accommodate thelateral extend of baffle 25 before reorientation thereof. Baffle 25includes first baffle element 26, a second baffle element 27, and asupport member 28, which may extend contiguously with the remainder oflead finger 20 from one side of baffle 25 to the other. FIG. 4illustrates a single baffle 25 along the length of lead finger 20;however, any number of baffles 25 may be placed along the length of leadfinger 20. Additionally, multiple lead fingers 20 may be modified toinclude a baffle 25. A selected lead finger 20 may be modified in width,thickness, or material composition in any manner necessary to providedesirable structural support for the chosen dimension of baffle 25. Theprevious discussion regarding the numerous modifications to a baffle,such as baffle 175 of FIGS. 7A through 7D, applies to baffles 25 aswell. In addition to a lead finger 20 being modified with a baffle 25 toserve as a flow restriction device, the lead finger 20 may also serveconventional, conductive functions. For example, the baffle 25 shown inFIG. 4 may, because of its vertical orientation, facilitate wire bondingto multiple levels of semiconductor die 60. In one embodiment,additional dam bars may be placed along the length of a modified leadfinger 20 to laterally connect the lead finger 20 with adjacent dummyleads 24 to provide additional structural support.

FIG. 5 illustrates that a baffle may be extended indirectly from supportor conductive members of a lead frame. In a particular embodiment,baffles 135 a, 135 b, and 135 c may extend from tie bars 30. Baffle 135a may be connected by neck 131 a to tie bar 30. Neck 131 a may be anylength necessary. Baffle 135 a may be connected to tie bar 30 by asingle neck 131 a or multiple necks 131 a. Neck 131 a may be bent,twisted, or manipulated in any manner desired along X-, Y- and Z-axes.For example, neck 131 a may be initially perpendicular to tie bar 30,but then later bent to a position such as that shown in phantom in FIG.5. Neck 131 a may also be angled vertically to any desired degree, aswell as twisted about its longitudinal extent. Baffle 135 a may includea first baffle portion and a second baffle portion, as in previouslydescribed embodiments, or baffle 135 a may serve solely as an upwardlyor downwardly extending baffle. Baffle 135 c is shown suspended from atie bar 30 through neck 131 c. Baffle 135 b is suspending from two tiebars 30 by necks 131 b, and may be twisted thereabout as well as bent ina symmetrical or asymmetrical manner to deflect resin flow. Baffles 135a, 135 b, and 135 c may, instead of extending from tie bars 30, extenddirectly or indirectly from paddles 50 or lead fingers 20.

A baffle may be added to a support or conductive member of a lead frameby either modifying the structure of such support and/or conductivemembers or by extending baffles indirectly off of the support orconductive members.

Heretofore, the baffle embodiments have been described as rectangularstructures. However, the baffles may be trapezoidal, circular,triangular, or any other shape. FIGS. 6A through 6D illustrate variousembodiments of non-rectangular baffles. FIG. 6A illustrates anembodiment where a baffle 165 a extends as a series of laterally spaced,comb-like fingers from the edge of a support or conductive member. FIG.6B depicts a baffle 165 b having a triangular configuration. FIG. 6Cdepicts a baffle 165 c having a circular configuration. FIG. 6D depictsa baffle 165 d having a semicircular configuration. “Support orconductive member,” as the phrase is used herein, encompasses paddles50, tie bars 30, lead fingers 20, or any other portion of a lead framethat lies in proximity to one or more semiconductor dice 60.

Any type of packaging technology that utilizes lead frames may use theembodiments of the present invention. The baffle embodiments may be usedto direct flow across the top surface of a semiconductor die 60 andadditionally across the bottom surface of the die paddle 50. In somesituations, flowing resin 70 under die paddle 50 would be undesirablesuch as when the die paddle 50 will be exposed to serve as a heat sinkand/or electrical ground. In such situations, the baffle embodiments maystill be utilized to direct resin flow to avoid flow under a die paddle50.

In an embodiment depicted in FIG. 11, a leads-over-chip (LOC) lead frame310 having lead fingers 20 extending over an active surface of asemiconductor die 60, as shown in broken lines, may be provided withbaffles 335 a on lead fingers 20, as well as baffles 335 b on one ormore projections 331 from the surrounding lead frame strip, S, as shown.In this embodiment, baffles 335 b may be deflected along a diagonal foldline F, as shown, to impede and redirect resin flow. Baffles 335 a maybe twisted about the longitudinal axes of their respective lead fingers20.

In a particular embodiment, flow-diverting structures may also beutilized to provide an increasing restriction as the flow rate of resin70 increases. For example, the degree to which a baffle intersects theflow of resin 70 may be determined by the flow rate of resin 70. Forexample, baffle 175 c shown in FIG. 7C may be used for this purpose. Ina particular embodiment, upper baffle 176 c and lower baffle 177 c maybe bent close together forming a partially opened clam shell. Baffle 175c may be made of a flexible or resilient spring-like material such thatthe angle of upper baffle 176 c, with respect to lower baffle 177 c, isdetermined by the pressure exerted by the flow of resin 70. The greaterdegree to which first baffle 176 c and second baffle 177 c are opened ordeflected, the greater the quantity of resin 70 restricted by the baffle175 c. Therefore, if resin 70 is flowing relatively slowly in thedirection indicated by arrow R, then baffle 175 c will remain open orundeflected and will present a substantial restriction to the flow;however, if resin 70 is flowing relatively quickly, then baffle 175 cwill collapse to a greater degree and provide a lesser restriction tothe flow of the resin 70. On the other hand, if resin 70 is flowing inthe opposite direction (or the orientation of baffle 175 c in thedrawing figure is reversed), a greater resin flow rate would result in agreater restriction as baffles 176 c and 177 c would be deflected andspread toward a more vertical position, transverse to resin flow. Baffle175 c is just one embodiment of a baffle that may increase therestriction of resin 70 proportional to the flow rate. The configurationof baffle 175 c may be used with a baffle 25, baffle 35, baffle 55,baffle 155, baffle 165, baffle 175, baffle 335, or others.

A variety of factors influence the flow rate of resin flowing in aparticular paddle-die set mold cavity. For example, a molding machinemay conventionally have a separate injection channel that mates witheach runner 17 (FIGS. 1 and 2) of a paddle-die set. Non-uniformities inthe molding machine injection channels may result in individual moldcavities receiving different flow rates. Where the injection channel ofa molding machine feeds multiple mold cavities in series, the flow rateexperienced by a first paddle-die set is going to be much higher than aflow rate experienced by a later paddle-die set at the end of theseries. A number of other factors may also affect the flow rate and theflow patterns at the different paddle-die set mold cavities.

In practicing an embodiment of the invention, a worker may intentionallyshort-shot the flow of resin 70 to a number of lead frames in strip formdisposed in a mold to determine the relative flow rates at differentpaddle-die set mold cavities of a lead frame strip. The worker may alsobe able to determine the locations in a mold cavity where the flow rateis differing or voiding. “Short-shotting,” as the term is used herein,refers to any process where the packaging of paddle-die sets isprematurely stopped. This may be accomplished by providing less thansufficient resin to encapsulate all of the paddle-die sets of the leadframe strip, or any other way known in the art.

In a particular embodiment, a baffle, such as baffle 35, baffle 55 a,baffle 55 b, baffle 155 a, baffle 165, baffle 165, baffle 175, or baffle335 may be attached to a support or conductive member and arrangedsubstantially transverse to a flow path of resin 70. The upper baffleand lower baffle of a baffle, such as baffle 35, baffle 55 a, baffle 55b, baffle 155 a, baffle 165, baffle 175, or baffle 335 may have anyangular orientation relative to a major plane of a semiconductor die 60or the direction of molding compound flow. In a particular embodiment,the upwardly and downwardly extending portions may have any non-parallelorientation relative to a bottom surface of semiconductor die 60 or thedirection of molding compound flow.

Once at least one lead frame strip has been short-shotted, then a workermay selectively modify one or more lead frames thereof to includeflow-diverting structures in the appropriate paddle-die sets of the leadframe strip. For example, where a lead frame strip has eight paddle-diesets, it may be that only five of those sets actually need modificationof the resin flow inside those cavities. Of those five paddle-die sets,each set may need to be modified in a unique way, or in a similarmanner. The newly modified lead frame strip may then be placed in themolding machine and then once again resin may be intentionallyshort-shotted into the lead frame strip. Therefore, a worker may be ableto iteratively modify lead frames of a lead frame strip and thenintentionally short-shot until the appropriate resin flowcharacteristics within each of the paddle-die set cavities is achieved.At that point, the lead frame strip may be mass-produced in modifiedform.

Additionally, modeling software may be utilized to predict whereshorting of resin flow may occur within the different paddle-die sets ofa lead frame strip. C-Mold is a non-limiting example of modelingsoftware that may be utilized to determine where in the paddle-die setsof a lead frame strip resin shorting will occur.

In other embodiments, the present invention may also be used for diepackaging that does not include lead frames. A few non-limiting examplesare flip-chip, BGA, PGA, chip-on-board (COB), and board-on-chip (BOC)packages. A few examples of BGA packages and variations thereof includeplastic BGA, enhanced plastic BGA, tape BGA, ceramic BGA, column ceramicBGA (also known as column grid arrays), flip-chip BGA, fine-pitch landgrid array, and fine-pitch BGA (also referred to as chip-scalepackages). The embodiments of the present invention apply to any type ofsemiconductor die packaging involving flowing resin to encapsulate atleast a portion of a semiconductor die.

FIGS. 8A through 8D illustrate an application to which an embodiment ofthe present invention may apply. In FIG. 8A, a plurality ofsemiconductor dice 260 have been attached to a substrate 210.Semiconductor dice 260 may be attached to substrate 210 by any meansknown in the art, such as by a liquid adhesive, an adhesive-coated tape,by discrete conductive elements such as balls, bumps, studs, pillars,columns or pins also serving as electrical connections, etc. Substrate210 may be a printed circuit board, a ceramic substrate, an array ofunsingulated interposer substrates, a wafer or other bulk semiconductorsubstrate, or any other substrate.

Semiconductor dice 260 may then be electrically connected (if notalready connected as noted above) to substrate 210, such as by wirebonds 240, as shown in FIG. 8B. FIG. 8B illustrates wire bonds 240across the top and bottom edges of semiconductor dice 260 (as thedrawing figure is oriented); however, wire bonds 240 may be placedaround any edge of semiconductor type die 260. As noted above, insteadof wire bonds 240, discrete conductive elements may be used, such as ina flip-chip package. In FIG. 8C, the assembly of semiconductor dice 260and substrate 210 has been placed in a mold M and clamped at an edge 212between two mating segments of the mold M. FIG. 8C also illustrates thatresin 270 may be flowed into the mold cavity as indicated by the arrowsand across the surface of substrate 210 from one edge to the other.Resin 270 may be used to underfill or encapsulate semiconductor dice260.

As shown in FIG. 8C, as resin 270 flows onto substrate 210, flow front271 having a configuration varying between 271 a, 271 b and 271 c as itprogresses across substrate 210 as shown is established. Resin 270 tendsto flow rapidly in the open areas between semiconductor dice 260 andflow relatively slowly over the tops of semiconductor dice 260. This mayresult in voids, knit lines, or pinholes forming over the top ofsemiconductor dice 260. The “top” of semiconductor dice 260 is relativeto substrate 210 and not necessarily indicative of the orientation ofsemiconductor dice 260. For example, when semiconductor dice 260 areconfigured as flip-chips, the “top” is the non-active face of theflip-chip wafers. A faster flow rate of resin 270 between semiconductordice 260 may also result in voids between solder balls or other discreteconductive elements in the standoff between semiconductor dice 260 andsubstrate 210 in flip-chip applications.

Substrate 210 may be conventionally placed in a mold (not shown) for thepurpose of flowing resin 270 over the substrate 210. In a particularembodiment of the invention depicted in FIG. 8D, an insert 230 is placedinside of the mold M and attached to a surface of substrate 210 on whichsemiconductor dice 260 are mounted. Insert 230 may include a pluralityof baffles 235, shown in FIG. 8D as being arranged in a grid pattern.Baffles 235 may be configured to reduce the flow rate of resin 270 inbetween the semiconductor dice 260 to a flow rate comparable to the flowrate of resin 270 over the tops of semiconductor dice 260. Flow front271, as depicted at 271 d, 271 e, and 271 f as the resin progressesacross substrate 210, illustrates how flow front 271 as depicted at 271a, 271 b, and 271 c may be modified by the use of insert 230.

In a particular embodiment, insert 230 may be designed for modifying theflow of resin 270, where resin 270 is injected on one side of substrate210, such as shown in FIG. 8D. In other embodiments, resin 270 may beinjected from multiple sides of substrate 210 or from above it. Insert230 may be modified accordingly to restrict the flow of resin 270between semiconductor dice 260. In other embodiments, wheresemiconductor dice 260 are not arrayed in a matrix, then insert 230 maybe configured to accommodate the arrangement of the semiconductor dice260.

Baffles 235 may be arced or stepped as necessary, and may be configuredwith comb-like protrusions as previously described with respect to FIG.6A to impede, but not prevent, resin flow through a particular area.

Embodiments of insert 230 may be attached to substrate 210 by a widevariety of means such as by an adhesive or by mechanically interlockingwith substrate 210. Substrate 210 may be modified to mechanicallyinterlock with an embodiment of insert 230. In a particular embodiment,insert 230 includes pins 232, which extend below the bottom surfaces ofinsert 230 and are operable for mating with corresponding holes formedin substrate 210. Insert 230 may be designed to mate with or mount tosubstrate 210 by resting upon substrate 210 and being affixed thereto byadhesive or mechanical means as noted, by being compressed betweensubstrate 210 and a wall of the mold cavity extending thereover, or byengaging with side walls of the mold cavity.

In an embodiment where insert 230 is held in place by substantiallycontinuous contact of the insert 230 with a wall of a mold member and asurface of substrate 210, it may be desirable to have suitably sized andconfigured windows W, as variously depicted in FIG. 10A, formed in thebaffles 235 to act as flow restrictors. In one such embodiment, theresin 270 allowed to flow across substrate 210 would be controlled bythe windows Win baffles 235. In that embodiment, baffles 235 wouldessentially form individual chambers around each semiconductor die 260.

FIG. 9 illustrates an enlarged view of the embodiment of insert 230shown in FIG. 8D. Baffles 235 may include baffles 235 a through 235 l,as shown in FIG. 9. An insert 230 may include any number of baffles 235,adapted to the number of semiconductor dice 260 mounted to substrate210. Insert 230 may, optionally, include a plurality of peripheralstructural supports 233. The structural supports 233 may interconnectouter ends of the different baffles 235 to each other and support thebaffles 235. Structural supports 233 may be any structure adapted forsupporting baffles 235. For example, structural supports 233 maycomprise a wall, a rod, or a wire. Structural supports 233 may besimilar or identical to baffles 235. Additionally, some of thestructural supports 233 may not present, such as around the perimeter ofinsert 230.

In a particular embodiment, baffles 235 are thin walls of rectangularcross-section and of lesser height than a distance between a surface ofsubstrate 210 and the wall of a mold member extending thereover. Inother embodiments, baffles 235 may exhibit a trapezoidal or a triangularcross-section, or any other geometric shape. Baffles 235 may alsocomprise horizontal rods as depicted in FIG. 10B, or laterally spacedvertical posts or struts as depicted in FIG. 10C, horizontally orvertically oriented spaced wires, wire mesh as depicted in FIG. 10D, orcombinations thereof. Baffles 235 may comprise any structure suitablefor retarding or directing the flow of a resin 270. Baffles 235 may haveany height, width, or thickness necessary. Baffles 235 may specificallyinclude, without limitation, any of the structures discussed withrespect to baffles 175, 165, 135, 55, 35, or 25.

Embodiments of insert 230 encompass any structure or structures that maybe placed on or attached to a substrate 210 and used to modify theconfiguration of flow front 271 of resin 270. In a particularembodiment, baffles 235 are not interconnected to each other.

Insert 230 may be designed to handle any arrangement of semiconductordice 260 and is not limited to an array of rows and columns of dice asshown. When it is desirable to only modify a portion of a flow front271, some baffles 235 may be removed or additional baffles 235 added.For example, due to mold variations, perhaps baffles 235 c, 235 f, 235i, and 235 l may not be necessary. Alternatively, baffles 235 c, 235 f,235 i, and 235 l may be designed to create less of a restriction thanthe other baffles 235, such as by reducing the height of those baffles.If increased restriction is desired, then, for example, an additionalbaffle 235 may be placed between baffles 235 g and 235 j. Or, the heightof the appropriate baffles may be increased. Baffles 235, with orwithout structural supports 233, may be placed anywhere on substrate210.

In some embodiments, insert 230 may be integral to substrate 210. In aparticular embodiment, substrate 210 is a circuit board and baffles 235are ridges or posts extending from the top surface of substrate 210. Anybaffle 235 structure operable to retard the flow of resin 270 may beincorporated into a circuit board. Where substrate 210 providesstructural support for baffles 235, then structural supports 233 may notbe necessary.

Similar to how short-shotting was previously discussed herein withrespect to lead frames, short-shotting may also be utilized as ananalytical technique with substrates 210. A prematurely stopped flow ofresin 270 may be evaluated to determine if a flow front 271 needs to bemodified by an insert 230, or if an existing insert requiresreconfiguration. An insert 230 may then be designed to meet the needs ofa certain mold, semiconductor dice and substrate combination, whichgenerates undesirable flow fronts 271.

Insert 230 may be made of any material compatible with retarding theflow of a resin 270, such as a metal, a stiff polymer, or a glass fiberlaminate.

In a particular embodiment, insert 230 is left in resin 270 while resin270 cures. Insert 230 may be destroyed whenever the semiconductor dice260 are separated or singulated from each other, such as by sawing ordicing. In another embodiment, insert 230 is removed prior to completecuring of resin 270 and may be reused. The same insert 230 may also beused for directing injection of multiple resins 270, such as anunderfill resin followed by an encapsulating resin.

Embodiments of the present invention may be utilized with wire bondingtechnologies, chip-on-board technology, board-on-chip technology,flip-chip technology, tape-automated bonding technology, BGA technology(including chip-scale packages), multichip module technology, or anyother packaging technology utilizing lead frames or other substrates inconjunction with encapsulating a semiconductor dice in a moldingcompound.

Examples of packages that may utilize embodiments of the presentinvention include: quad flat packages, low profile quad flat packages,thin quad flat packages, quad flat packages, no-lead thin small outlinepackages, thin shrink small outline packages, small outline packages,shrink small outline packages, dual in-line packages, shrink dualin-line packages, single in-line packages, shrink single in-linepackages, and shrink zig-zag in-line packages.

Semiconductor dice 60 may be any type of dice and may be used for anyapplication, as packaged in accordance with embodiments of theinvention. Embodiments of the present invention may be used not onlywith semiconductor devices, but with other devices such as passivefilters, detector arrays, and MEMS devices.

The present invention may be embodied in other specific forms withoutdeparting from its characteristics. The described embodiments are to beconsidered in all respects only as illustrative and not restrictive. Thescope of the invention is, therefore, indicated by the appended claimsrather than by the foregoing description. All changes that fall withinthe meaning and range of equivalency of the claims are embraced withinthe scope thereof.

What is claimed is:
 1. A lead frame strip for use in encapsulating aplurality of electronic devices disposed in at least one mold cavitywith a flowable molding compound, the lead frame strip comprising: aplurality of lead frames, wherein each lead frame of the pluralitycomprises: a plurality of lead fingers located in proximity to anintended location of at least one electronic device when secured to thelead frame; at least one paddle sized and configured to receive at leastone electronic device thereon; and at least one enlarged memberproximate the at least one paddle, the at least one enlarged memberpositioned and configured with respect to an intended direction of flowof a molding compound past the lead frame during encapsulation thereofto impede flow of the molding compound past at least one surface of theat least one electronic device.
 2. The lead frame strip of claim 1,wherein the at least one enlarged member is at least a portion of a tiebar securing each lead frame to a surrounding support structure of thelead frame strip.
 3. The lead frame strip of claim 1, wherein the atleast one electronic device comprises at least one semiconductor device.4. The lead frame strip of claim 3, wherein the at least onesemiconductor device comprises a plurality of semiconductor devices. 5.The lead frame strip of claim 1, wherein the at least one enlargedmember comprises at least a portion of a lead finger.
 6. The lead framestrip of claim 5, wherein the lead finger is selected from a groupconsisting of a dummy lead, a ground lead, or a hot lead.
 7. The leadframe strip of claim 1, wherein at least a portion of the at least oneenlarged member is oriented in substantially non-parallel orientation toa direction of flow of the molding compound past the at least oneelectronic device.
 8. The lead frame strip of claim 7, wherein the atleast a portion of the at least one enlarged member is at least one ofplanar, arcuate, or stepped.
 9. The lead frame strip of claim 1, whereinthe at least a portion of the at least one enlarged member is configuredto deflect in response to contact of a flow front of the moldingcompound therewith.
 10. The lead frame strip of claim 1, wherein the atleast a portion of the at least one enlarged member is sufficientlyrigid so as to not substantially deflect in response to contact of aflow front of the molding compound therewith.
 11. The lead frame stripof claim 1, wherein the at least one enlarged member is positionedproximate a side of the at least one electronic device orientedsubstantially parallel to the intended direction of flow of the moldingcompound.
 12. The lead frame strip of claim 1, wherein the at least oneenlarged member is positioned proximate a side of the at least oneelectronic device substantially facing the intended direction of flow ofthe molding compound.
 13. The lead frame strip of claim 1, wherein theat least one enlarged member includes a first portion and a secondportion extending substantially in mutually opposing directionssubstantially transverse to the intended direction of flow of themolding compound.
 14. The lead frame strip of claim 1, wherein the atleast one enlarged member is located within a boundary of a packagingenvelope to be formed about the at least one electronic device afterencapsulation thereof with the molding compound.
 15. An assembly for atleast partial encapsulation of semiconductor devices, the assemblycomprising: a substrate bearing a plurality of semiconductor dice in amutually spaced relationship; and a grid structure secured to one sideof the substrate and comprising a plurality of baffles, wherein at leastsome of the plurality of semiconductor dice are separated by bafflesdisposed therebetween.
 16. The assembly of claim 15, wherein each of theplurality of baffles comprises a member extending substantiallytransverse to a major plane of the substrate.
 17. The assembly of claim15, further comprising a mold comprising a segment extending over thesubstrate, and wherein the grid structure is secured between a surfaceof the substrate and a wall of the segment of the mold extendingthereover.
 18. The assembly of claim 17, wherein a height of at leastsome of the baffles is less than a distance between the surface of thesubstrate and the wall of the segment of the mold.
 19. The assembly ofclaim 18, wherein a height of at least some of the baffles issubstantially equal to a distance between the surface of the substrateand the wall of the segment of the mold, and further comprisingapertures through the at least some of the baffles.
 20. A substrate forthe mounting of semiconductor dice thereon, the substrate comprising: aplanar member; a matrix of die attach spots located on a surface of theplanar member; and a matrix of flow restriction structures attached tothe planar member, at least some of the flow restriction structurescircumscribing at least some of the die attach spots.
 21. The substrateof claim 20, wherein the matrix of flow restriction structures isintegral to the substrate.
 22. The substrate of claim 21, wherein thematrix of flow restriction structures comprises ridges formed on thesurface planar member of the substrate.
 23. The substrate of claim 20,wherein the matrix of flow restriction structures comprises a matrix oflaterally separated posts extending orthogonally from the surface of theplanar member of the substrate.